This present invention is directed to a prosthetic cup assembly which is disclosed in the context of a hip prosthesis.
It is known to provide an acetabular cup assembly that includes a metal shell component for attachment to an acetabulum to replace the natural socket and a plastic bearing component that is inserted into the shell to provide a bearing surface for receiving a femur ball prosthesis element. See for example, U.S. Pat. No. 5,049,158, to John A. Englehardt et al., the disclosure of which is expressly incorporated herein by reference. In addition, traditional bearing components include a built-up lip around a portion of the bearing surface. See for example, U.S. Pat. Nos. 5,282,864 and 5,413,603 to Noiles et al., the disclosures of which are also expressly incorporated herein by reference
According to the present invention a prosthetic cup assembly for use in a joint such as a hip joint is provided. The prosthetic cup assembly comprises a shell with a concave inner surface and a liner that is taper mounted to the inner surface of the shell. The cup assembly also includes a separate bearing securely attached inside the liner. Specifically, the inner surface of the shell provides, at its outer extent, a female taper opening into the shell. A male taper positioned on an outside surface of the liner engages the female taper to hold the bearing in the cup-like shell.
In another embodiment of the present invention, a kit is provided for the replacement of a cup portion of a bone of a joint. The kit comprises a shell formed with a concave inner surface providing, at its outer extent a female taper, and at least two bearing/liner subassemblies. The subassemblies include a bearing component mounted within a liner. The bearing component provides an internal cavity for receiving a ball and an opposite exterior coupled to an inside surface of the liner. The liner also has an outer surface providing a male taper sized for receipt by the female taper. The engagement of the female taper on the male taper provides the mechanical connection between the shell and the subassembly.
In yet another embodiment of the present invention, a method is provided for assembling a bearing/liner subassembly for a ball-joint type prosthetic appliance. The method includes the steps of cooling a bearing component that has an exterior with a normal pre-determined radius at a temperature sufficient to shrink the radius of the exterior and placing the cooled bearing component into a liner to form a bearing/liner subassembly. The liner has an inside surface facing the bearing component and an outer surface providing a male taper. The inside surface of the liner has a radius that is greater in size than the reduced radius of the bearing component and less than the normal pre-determined radius of the bearing component. Next, the subassembly is warmed to a temperature sufficient to return the exterior of the bearing component to the normal pre-determined radius. Thus, the bearing component is mounted in a fixed and locked position within the liner. The subassembly is then inserted into a shell that is formed with a generally hemispherical concave inner surface providing, at its outer extent a female taper for receiving the male taper of the liner. The engagement of the female taper on the male taper provides the mechanical connection between the shell and the liner.
In still another embodiment of the present invention, a prosthetic component assembly is provided for use in fixation to bone. The assembly includes a prosthetic component assembly for use in fixation to bone, the assembly comprising a shell formed with an inner surface providing at its outer extent a female taper, a liner formed with an inner end, an opposite outer end, an inside surface and an opposite outside surface extending between the inner and outer ends, a male taper positioned to lie on the outside surface adjacent the outer end for receipt by the female taper, the engagement of the female taper on the male taper providing a mechanical connection between the shell and the liner, and a bearing component. The bearing component is formed for coupling with the liner and has an internal cavity and an opposite exterior, the exterior being formed for engagement with the inner surface of the liner.
In a further embodiment of the present invention, a prosthetic cup assembly for use in fixation to bone is provided. The assembly includes a shell defining a shell cavity, the shell being configured with (i) an inner surface having a female taper, and (ii) a locking recess defined in the inner surface of the shell. The assembly further includes a bearing defining a bearing cavity adapted to receive a prosthetic ball therein, the bearing is configured with (i) an outer surface having a male taper, and (ii) a locking member extending outwardly from the outer surface of the bearing. When the bearing is positioned within the shell cavity, the male taper and the female taper engage each other so as to provide a first connection between the bearing and the shell. Further when the bearing is positioned within the shell cavity, the locking member is located within the locking recess so as to provide a second connection between the bearing and the shell.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.